On 14/09/17 09:54, George News wrote:
Hi,
Continuing with my issues with transactions, next question ;)
question*s* :-)
1) If I get a model as a result of a multiunion or a set of entities
from a read transaction, will I be able to use this model after the
transaction ends (i.e. in a SPARQL request).
MultiUnion union = new MultiUnion()
dataset.begin(ReadWrite.READ);
union.addGraph(dataset.getNamedModel("A").getGraph();
union.addGraph(dataset.getNamedModel("B").getGraph();
Model m = ModelFactory.createModelForGraph(union);
dataset.end();
// Execute SELECT SPARQL over m without opening a read transaction
Will it work? What data is included?
> Will it work?
No.
MultiUnion is a view - it does not actually have the triples, only
pointers to the graphs, and the graphs are views of the dataset, which
is where the data really is.
2) Suppose I have a webservice exporting read/write functionality from a
TDB. Every request opens a transaction over the TDB. If the request is
taking too long the HTTP client closes the connection. What happens with
the transactions? From my understanding, once the connection from the
client is closed, all resources for the call are freed at the server and
then the transactions will be somehow aborted and released. Am I right?
If the client closes the connection, the server does not know until it
tries to use the connection. If written correctly, the server needs to
clear up when it can.
https://stackoverflow.com/questions/2962196/detecting-client-disconnect-in-tomcat-servlet
Txn does the clearup:
https://jena.apache.org/documentation/txn/txn.html
or long way:
dataset.begin(WRITE)
boolean commitDone = false;
try {
... action ...
... some IOException on the response connection ...
dataset.commit()
commitDone = true;
} finally {
if ( ! commitDone )
dataset.abort();
dataset.end();
}
though
dataset.begin(WRITE)
try {
... action ...
dataset.commit()
} finally {
dataset.end();
}
works just fine - end() forces an abort if no commit or abort was called.
ARQ has query timeouts.
Thanks a lot for you invaluable help. I feel really sorry for bothering
so much, but I'm suffering from some stability issues on the developed
system (mainly memory leaks, etc.) and need to properly understand if
I'm making things the right way.
Regards,
Andy
